Evaluate the use of antiserum against feline oncornavirus associated cell membrane antigen (FOCMA) and inactivated tumor cells in the treatment of thymic lymphoma and acute lymphoblastic leukemia in cats. This will involve the production of large pools of antiserum to FOCMA and the use of tissue culture to develop tumor cell lines. Treated animals will be monitored at intervals of approximately two weeks with evaluation of their clinical status, and various in vitro and in vivo assays including FOCMA antibody titers and blast transformation with Con A, lipopolysaccharide, and FOCMA antigen.